Speed test on a freshly booted machine is 100/100Mbps ... very often after viewing a youtube video in Firefox, this Speed test can slow down to below 20Mbps which results in a poor streaming experience ... I have a 150/150 fiber connection and the modem speed test doesn't change ... nothing to do with anything downstream ... not running anything else except FF ... always running with the latest up to date version(s) ... things of note: the process count goes up when this occurs ... even if FF is restarted it doesn't resolve this issue ... only a reboot resolves the issue ... when rebooting there is always some UNKNOWN process that needs to be manually terminated before the reboot process runs. I suspect one of the multilayered (FF appears to open multiple sessions with streaming) processes may be getting widowed and left running and not releasing resources which causes less and less bw to be available ... this appears to occur mostly if I either Fast Forward or try to click forward or backward on a stream timeline suggesting to me that the current timeline may not be closing properly ... process manager doesn't reveal any processes linked to firefox but there are numerous svchost processes which I expect may be involved Are there other ways/tools to narrow down this issue so the Mozilla team might be able to fix this ... I use FF exclusively but this has become more and more of an annoyance. My i7 2TB 2.6GHz 8GB laptop is unable to move beyond W7 64b pro but I have had the same experience on a W10 64b Pro machine so very skeptical that this is an OS related issue. Ultimately if FF kept track of the PIDs it opens it should be able to force them to close if they refuse to close on their own. Kill Process tree ... or ... perhaps provide a log that is user accessible identifying opened PIDs so that a user could manually kill widow processes without having to reboot.